The technical province of this invention concerns safety measures against fires in buildings.
The prior art has provided numerous devices in the form of duct-closing valves or trapdoors that operate in the event of an outbreak of fire in premises inside buildings having controlled mechanical ventilation, in which it is desired to avoid propagation of the flames through the ducts. Conversely, subsequent to a fire, it may be necessary to activate special ducts which are normally closed by valves or trapdoors, by opening the same in order to clear rooms, floors and corridors of smoke.
Prior art devices are complicated and costly and offer little facility for convenient adjustment of the throughput in the case of flame-arresters, nor sufficient versatility of the component parts to enable either flame-arresters, or smoke-clearing trapdoors or valves, to be devised.